1. Field of the Invention
The present invention relates generally to valves for modules of semiconductor processing equipment, and more particularly to a single shaft actuator mounted on two cradle plates and carrying dual slot valves, and to methods of implementing such valves between separate chambers of semiconductor processing equipment, wherein at least one pivot of one cradle is vertically aligned with a mounting surface of a particular valve upon closure of the particular valve against a seal surface of the slot to provide movement of the particular valve perpendicularly toward the seal surface, and wherein operations may continue in one chamber during servicing of the other chamber, which semiconductor processing equipment may be a multi-chamber vacuum system.
2. Description of the Related Art
In the manufacture of semiconductor devices, multiple process chambers are interfaced to permit transfer of substrates or wafers, for example, between the interfaced chambers. Such transfer is via transport modules that move the wafers, for example, through slots or ports that are provided in the adjacent walls of the interfaced chambers. For example, transport modules are generally used in conjunction with a variety of substrate processing modules, which may include semiconductor etching systems, material deposition systems, and flat panel display etching systems. Due to the growing demands for cleanliness and high processing precision, there has been a growing need to reduce the amount of human interaction during and between processing steps. This need has been partially met with the implementation of transport modules which operate as an intermediate handling apparatus (typically maintained at a reduced pressure, e.g., vacuum conditions). By way of example, a transport module may be physically located between one or more clean room storage facilities where substrates are stored, and multiple substrate processing modules where the substrates are actually processed, e.g., etched or have deposition performed thereon. In this manner, when a substrate is required for processing, a robot arm located within the transport module may be employed to retrieve a selected substrate from storage and place it into one of the multiple processing modules.
As is well known to those skilled in the art, the arrangement of transport modules to xe2x80x9ctransportxe2x80x9d substrates among multiple storage facilities and processing modules is frequently referred to as a xe2x80x9ccluster tool architecturexe2x80x9d system. FIG. 1 depicts a typical semiconductor process cluster tool architecture 100 illustrating the various chambers that interface with a transport module 106. Transport module 106 is shown coupled to three processing modules 108a-108c which may be individually optimized to perform various fabrication processes. By way of example, processing modules 108a-108c may be implemented to perform transformer coupled plasma (TCP) substrate etching, layer depositions, and/or sputtering.
Connected to transport module 106 is a load lock 104 that may be implemented to introduce substrates into transport module 106. Load lock 104 may be coupled to a clean room 102 where substrates are stored. In addition to being a retrieving and serving mechanism, load lock 104 also serves as a pressure-varying interface between transport module 106 and clean room 102. Therefore, transport module 106 may be kept at a constant pressure (e.g., vacuum), while clean room 102 is kept at atmospheric pressure. To prevent leaks between modules during pressure varying transitions, or to seal off a processing module from transport module 106 during processing, various types of gate drive valves are used to isolate the various modules.
For more information on gate drive valves, reference may be made to U.S. Pat. No. 4,721,282, which is hereby incorporated by reference. Another such gate drive valve is shown in U.S. Pat. No. 5,667,197, in which a prior art valve housing is shown having two port openings, and only one valve for one of the two port openings. Thus, it is not possible to close the port that does not have an associated valve. Also, the gate plate valve of the ""282 Patent is shown for closing a port between abutting transport and process chambers, and no intermediate valve housing is provided. A drive assembly for the gate plate moves the gate plate in one continuous motion in a vertical path and in a rotating arc toward the internal port to effect a seal or closure of the internal port.
U.S. Pat. No. 5,150,882 shows one valve between various chambers of a treatment system, including between a decompression chamber and an etching chamber. Such one valve is driven for engagement and disengagement with a gate aperture by one air cylinder and a toggle arrangement such that stopper plates hit rollers with considerable impact. Initial vertical movement of a fitting plate is changed to horizontal movement by the link that is rotated counterclockwise, such that the gate moves toward the gate aperture. For the ""882 Patent to avoid problems of the prior art, the stopper plates are made from a double boride hard alloy. Further, the single motion of the one air cylinder is not stopped, but instead continues its driving operation after the abutment of the stopper plates with the rollers. Thus, in addition to requiring special materials, the ""882 Patent does not provide two valves between adjacent processing chambers.
Other valves for cluster tool architecture systems include a separate actuator for each of two valves, which tends to increase the width of a valve actuation housing or, when attempts are made to reduce such width, to restrict the location at which force is applied by the actuators to the valves. Also, such valves require a separate bellows for each of the two separate actuators. Because the cost of such bellows is substantial (e.g., in the range of $800.00 to $1000.00 each in year 2000 U.S. dollars), it is costly to require two bellows. Further, each such separate actuator is generally driven by a separate pneumatic cylinder, which also increases costs when one separate actuator is required for each of the two valves.
Still other valves for cluster tool architecture systems include one cradle having one pivot for mounting one actuator, wherein the one pivot is not movable into alignment with the valve seal surfaces of both of two valves carried by the one actuator.
In view of the forgoing, what is needed is a valve assembly between adjacent process or transport chambers, wherein the valve assembly has one shaft for dual valves, thus reducing the cost of the assembly by eliminating one bellows, and wherein one shaft is mounted on two pivotally-mounted cradles, and wherein at least one pivot of one cradle is vertically aligned with a mounting surface of a particular valve upon closure of the particular valve against a seal surface of the slot to provide movement of the particular valve perpendicularly toward the seal surface, and wherein one pneumatic drive of a two actuator dual valve is eliminated, and wherein operations in one such chamber may continue while servicing, for example, is performed in the other chamber.
Broadly speaking, the present invention fills these needs by providing a single shaft carrying a dual-sided slot valve in a housing between adjacent chambers or modules, such as a transport chamber and a process chamber. Separate selectively closed and opened valves are provided for each of two valve housing ports or slots, such that one housing port adjacent to the process chamber or one housing port adjacent to the transport chamber, for example, may be selectively closed while the other port remains open. For example, the selectively closed valve facilitates maintaining a vacuum, for example, in a transport chamber while an adjacent process chamber is opened to the atmosphere to allow servicing to be performed. As a result, substantial periods of downtime are avoided in that no pump-down cycle is needed to bring the transport chamber to a desired vacuum after servicing the process chamber, and no other operations need be performed on the transport chamber due to the servicing of the process chamber.
Also, with the valve to the transport chamber closed so that the transport chamber is at vacuum, the passage of debris (such as broken wafers) from the open process chamber may be blocked by the open valve to the process chamber so that such debris does not contaminate the transport chamber. Thus, in general, only the valve door next to the process chamber need be replaced during servicing after it becomes corroded, and the transport chamber may remain at vacuum during such replacement.
Further, the dual-sided slot valve is provided with these advantages while initially allowing easy access to one or both open valve(s) for performing service on the open valves. Such easy access is provided by a single shaft operated by a first drive mounted on a primary cradle, and operated by second and third drives mounted on a secondary cradle. To close one valve, the first drive is retracted to rotate the primary cradle, and the second drive is extended to rotate the secondary cradle on the primary cradle. The first and second drives stop with the one valve closed and the other valve in an open, but not laterally-spaced (i.e., not vertically-spaced), position relative to the respective port. If both valves are to be serviced, the first drive and the second drive are extended against stops to position both cradles so as to hold the single shaft centered in an open-shaft position and maintain an open position of each valve. In this open-shaft position the open valve or valves may be reached by a gloved hand of a worker for service.
The third drive may function to move the single shaft and cause both of the valves to move laterally (e.g., downwardly) away from the open position and away from the respective ports. The downwardly-moved open valves expose the seal surfaces around the ports, which permits cleaning of the seal surfaces, for example. Due to the vertical distance between the downwardly-moved valves and an access opening (which is normally closed by a lid), it is generally difficult for the protective glove of the worker to reach the valve for service after the vertical movement. In the downwardly-moved position, however, the valves do not interfere with the ability to clean around the valve doors, including the surfaces against which the doors seal.
Additionally, only the one shaft is provided for both of the slot valve doors so as to reduce the clean room real estate occupied by the valve housing between the adjacent transport and process chambers, for example. Also, such one shaft applies force to each of the slot valve doors at a central location of the slot valve door, which reduces the force required to maintain the slot valve door closed. Further, with only one shaft, only one bellows is required, as compared to the valve assemblies that have two actuators and that thus require two bellows.
In addition, with the single shaft mounted on two cradle plates and carrying the dual-sided slot valve, at least one pivot of one cradle is vertically aligned with a mounting surface of a particular valve upon closure of the particular valve against a seal surface of the slot to provide movement of the particular valve perpendicularly toward the seal surface.
It may be understood, then, that while normal operations continue in one chamber of two adjacent chambers, many types of servicing may be performed in the other of the two chambers. Such servicing may, for example, include removing broken pieces of wafers from a chamber or the valve housing, cleaning the seal surface of a port, cleaning the interior of a chamber, and removing and replacing a member of a valve (e.g., a door or an O-ring) that effects the seal with the seal surface. These and other operations for maintaining such chambers in normal operation for semiconductor processing, for example, are referred to herein as xe2x80x9cservicing,xe2x80x9d or xe2x80x9cservice.xe2x80x9d
Other aspects and advantages of the invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.